JPH11308828A - Switched reluctance motor and its control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To concentrate magnetic flux flowing into a rotor-side wall surface on the side surfaces of a protrusion when a salient rotor pole begins to face a salient stator pole, to increase magnetic flux flowing-in in the peripheral direction, and to increase the torque and efficiency, by forming a protrusion stretching in a rotating side peripheral direction and having a plane at its rotating side end, at the tip of each salient rotor pole. SOLUTION: A reluctance motor rotates by switching-controlling current flow into exciting windings 5 wound on salient stator poles 3 according to the positional relation between the rotor 1 and the stator 2. Here, a protrusion 6 extending in a rotating peripheral direction is provided at the tip of each salient rotor pole 4, and its tip is formed into a plane. And magnetic flux, which is generated by current flow into the exciting windings 5 when a salient rotor pole 4 begins to face a salient stator pole by the rotation of the rotor 1, and flows into the wall surface of each salient rotor pole 4 from a salient stator pole 3 through an air gap, is concentrated on the protrusion 6. Consequently, it becomes possible to increase the peripheral-direction component of a magnetic flux density in the vicinity of the peripheral surface of the rotor 1, and to increase its torque.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a switched reluctance motor (hereinafter, referred to as an SR motor), and more particularly to a high-efficiency drive and control method using no sensor.

[0002]

2. Description of the Related Art As shown in FIG. 16, a conventional SR motor comprises a rotor 1 and a stator 2 in which magnetic thin plates such as silicon steel plates are laminated. A rotor salient pole 4 and a stator salient pole 3 are formed on the rotor 1 and the stator 2, respectively, and a winding 5 is wound around each stator salient pole 3 on the stator 2 side.

The control circuit 13 detects the position of the rotor salient pole 4 of the rotor 1 by a sensor or the like, supplies a voltage pulse to the winding 5 in accordance with the position of the rotor 1, and sequentially turns the stator salient pole 3. Excite. Due to the magnetic force of this excitation,
Each rotor salient pole 4 of the rotor 1 is attracted, and the rotor 1 rotates.

As a conventional technique relating to the SR motor, for example, a rotor having a shape as shown in FIG. 16 is generally used. As a special shape, an SR motor (conventional example 1) disclosed in Japanese Patent Application Laid-Open No. 8-126273 protrudes from the tip of each salient pole of the rotor along the rotation circumferential direction, as shown in FIG. In addition, protrusions that become narrower toward the tip end are provided on both sides, and by reducing the saturation magnetic flux amount of the rotor salient poles, it is possible to avoid the appearance of torque peaks and suppress torque fluctuations. is there.

Also, when driving this SR motor,
In order to switch the timing of energizing each winding, it is necessary to accurately detect the rotor position, and an axial position sensor for detecting the rotational position of the rotor has been used. Sensorless control technology that does not require a shaft position sensor has been proposed and studied in the past. For example, an SR motor control device (conventional example 2) disclosed in Japanese Patent Application Laid-Open No. 63-202294 samples a current after a time set by a sampling time circuit after a voltage is applied to a winding, and outputs the current to a reference signal. The deviation from the desired rotor position is obtained by comparison, and the excitation current is controlled by controlling the power supply circuit in response to the error signal. Therefore, a complicated circuit as shown in FIG. 1A is used. The shape of the rotor of Conventional Example 2 is shown in FIG.
As shown. This is a standard type as shown in FIG. 16, in which the side surfaces of the salient poles of the rotor are vertical, and there are no tapered protrusions on both sides of the tip of the rotor salient poles as in Conventional Example 1.

[0006]

FIG. 16 is a side sectional view of a conventional standard SR motor. According to the rotor 1 having such a shape, the rotational torque generated in the process of opposing the rotor salient poles 4 and the stator salient poles 3 is sufficiently obtained in consideration of the state of the magnetic flux lines flowing from the stator salient poles 3 to the rotor salient poles 4. It has a shape that cannot be obtained. Hereinafter, the cause of the torque loss will be described with reference to FIG.

In order for the reluctance motor to obtain, for example, a rotational torque indicated by an arrow in a counterclockwise direction, a circumferential component of the magnetic flux density needs to act on the surface of the rotor salient pole 4. The instantaneous reluctance torque at an angle α between a given rotor 1 and stator 2 is given by Maxwell's stress equation:
It is represented by the following equation (1).

[0008]

(Equation 1)

From the equation (1), to increase the rotational torque, a magnetic field must be obliquely incident on the rotor outer peripheral surface 7 (r surface), and on the rotor side wall surface 8 (θ surface). The larger the vertical component of the magnetic field incident on the surface, the better. Also,
When the magnetic field acts near the outer periphery of the rotor, the rotational torque can be increased. However, in the rotor shape conventionally used, the rotor side wall surface 8 has a linear shape as shown in FIGS. FIG. 18 shows an example of a magnetic flux diagram by magnetic field analysis in this shape.

FIG. 18 shows a case where the rotor salient poles 4 and the stator salient poles 3 do not face each other. If the rotor salient poles 4 and the stator salient poles 3 face each other, the magnetic flux flowing into the rotor outer peripheral surface 7 is mostly composed of the radial component of the rotor and does not contribute to the rotational torque. In addition, the rotor salient pole outer surface 7, which is not opposed, is incident on the surface obliquely from above,
Although a rotating torque is generated, the opposing area increases as the rotor rotates, and the magnetic field component contributing to the rotating torque decreases, and eventually becomes zero. On the other hand, the inflow of the magnetic flux to the rotor side wall surface 8 side is inclined and flows into the side wall surface 8 and includes both the circumferential and radial components. Of these, the circumferential direction (θ) component determines the rotational torque determined by equation (1). As shown in FIG. 18, when the rotor salient poles 4 and the stator salient poles 3 do not face each other, many circumferential components are included. However, when the rotor 1 rotates and the two begin to face each other, the inflow angle gradually increases. In the radial direction, causing a decrease in rotational torque. As described above, there is a problem that the rotation torque is greatly reduced with the rotation of the rotor 1 and the fluctuation of the torque is increased.

Further, in the SR motor disclosed in the conventional example 1, the rotor protrudes along the rotation circumferential direction at the tip of the rotor.
In addition, since the protrusion that becomes narrower toward the front end side is provided, when the rotor salient pole and the stator salient pole gradually start to oppose from each other, the inflow magnetic flux gradually increases with the rotation of the rotor. As a result, it is possible to suppress a sudden increase in magnetic flux in the salient poles of the rotor and a large fluctuation in torque as in the related art. However, the inflow position of the magnetic flux from the stator salient poles is limited to the opposed rotor salient pole faces, and the inflow angle of most of the magnetic flux is in the radial direction, which has an adverse effect on the rotation torque generation of the rotor. However, there is a problem that the motor efficiency is reduced.

Further, in the SR motor operation control disclosed in the conventional example 2, the winding current is sampled. However, in the SR motor having the conventional rotor structure, the winding current which fluctuates with the rotation of the rotor is changed. Since the amount of change is small, there is a problem that a large number of ripples are superimposed on the current, and the position determination accuracy is greatly reduced.

The present invention has been made to address such a problem. By changing the shape of the tip of the rotor salient pole 4, the magnetic flux inflow angle is changed in the circumferential direction to reduce the fluctuation of the rotor rotation torque. It is an object of the present invention to provide an SR motor that suppresses, increases the rotational torque as a whole, improves efficiency, and enables highly accurate sensorless control with a simple circuit configuration.

[0014]

Means for Solving the Problems In order to achieve the above object, the following means are taken in the SR motor of the present invention.

According to the first aspect of the present invention, the surface of the rotor salient pole in the direction of rotation extending in the rotation side circumferential direction forms a flat protrusion at the tip of the rotor salient pole, and the rotor salient pole and the stator salient pole begin to face each other. In this case, the magnetic flux flowing into the rotor side wall concentrates on the side of the protrusion,
The magnetic flux is changed to the outer circumferential direction of the rotor, and the inflow magnetic flux in the circumferential direction increases, so that the torque decrease is suppressed.

According to a second aspect of the present invention, an appropriate ratio between the height of the protrusion and the height of the rotor salient pole is provided.
Gives an appropriate value of the aspect ratio of the protrusion. This can reduce the amount of magnetic flux flowing from the stator salient poles and avoid excessive concentration of magnetic flux density when passing through the protruding portion, thereby alleviating magnetic flux saturation during high-speed rotation and high-torque rotation. A decrease in torque can be avoided.

According to a fourth aspect of the present invention, the length of the protrusion extending in the circumferential direction of the tip of the rotor salient pole is changed in the direction of the rotation axis.
This makes it possible to shift the maximum rotation torque generation timing in the direction of the rotation axis, reduce the exciting force applied to the stator when the maximum rotation torque is generated, and reduce vibration due to torque fluctuation.
Noise can be suppressed.

According to a fifth aspect of the present invention, a protrusion is provided in the circumferential direction of the tip of the rotor salient pole, and the protrusion is also extended in the counter-rotating circumferential direction at the tip of the stator salient pole. Thus, the magnetic flux flowing into the rotor surface on the side facing the stator is also changed in the circumferential direction, and an increase in the rotational torque can be achieved.

According to a sixth aspect of the present invention, the rotor surface has a projection extending in the circumferential direction of the rotor salient pole tip, and the rotor surface excluding the side surface facing the stator salient pole and the side wall surface having the projection is non-magnetic. Cover with body. As a result, the inflow position of most of the magnetic flux on the rotor surface is limited to the surface on the side facing the stator and the side surface on the protruding portion, and the leakage of the magnetic flux to other surfaces can be suppressed, which is effective for rotating the rotor. Power can be increased, and it is possible to contribute to the improvement of torque.

According to a seventh aspect of the present invention, in the protruding portion extending in the circumferential direction of the rotor salient pole tip, the angle of the connecting portion on the shaft side of the rotor side wall at the root is made gentle. This allows
When the magnetic flux passing through the protruding portion flows into the rotor body, the direction of the magnetic flux is greatly changed, and the tendency that the magnetic flux concentrates at the corners can be suppressed, and the magnetic saturation when the magnetic flux passes through the rotor can be suppressed. As a result, more magnetic flux can be supplied, and an improvement in torque is achieved.

An eighth aspect of the present invention relates to a method for controlling a switched reluctance motor as described above. It has a protrusion extending in the circumferential direction of the rotor salient pole tip, and the magnetic flux from the stator in the initial stage of opposition between the stator and the rotor intensively flows in from the protruding surface of the rotor tip. Since the rotor position can be determined by detecting the change, the detection accuracy of the control method that does not use a sensor can be significantly improved without using a complicated circuit as in the past, and the motor efficiency is improved. Can be greatly contributed to.

[0022]

FIG. 1 is a sectional view showing a relationship between a stator 2 and a rotor 1 according to a first embodiment of the present invention. As shown in FIG. 1, the reluctance motor includes a stator 2 which is formed of a laminated magnetic material such as a silicon steel plate and is fixed to a casing, and a rotatable magnetic material such as a silicon steel plate which is rotatably arranged inside the stator 2. And the rotor 1 configured.

On the inner peripheral side of the stator 2, a number of stator salient poles 3 arranged at equal intervals are formed. Also,
A large number of rotor salient poles 4 arranged at equal intervals are also formed on the outer peripheral side of the rotor 1. An exciting winding 5 is wound around a stator salient pole 3 provided on the stator 2.

In the SR motor, the rotor salient poles 4 are attracted in the direction facing the stator salient poles 3 by the magnetic force generated by sequentially energizing the exciting windings 5, and the rotor 1 rotates. Therefore, the rotation amount of the rotor 1 is detected by a rotary encoder or the like, and the stator 2 and the rotor 1 are detected.
Depending on the positional relationship between them, the timing of energizing the exciting winding 5 is switched by the control circuit 13 to rotate continuously, thereby fulfilling the function as a motor.

Here, the rotor 1 according to the first embodiment is described.
As shown in FIG. 1, the structure (1) has a protrusion 6 extending in the circumferential direction of rotation at the tip of the rotor salient pole 4, and the tip is flat. FIG. 2 is an enlarged view of the main part. When the stator salient pole 3 and the rotor salient pole 4 do not face each other, a magnetic force is generated by energizing the exciting winding 5, and the magnetic flux is generated from the tip of the stator salient pole 3. After passing through the space, the air flows into the rotor 1 again from the rotor salient poles 4. At this time, the magnetic flux flows in from the rotor outer peripheral surface 7 and the side wall surface 8 facing the stator salient pole 3. Since the magnetic flux flowing from the rotor side wall surface 8 is concentrated at the tip of the protrusion 6, the circumferential component of the magnetic flux density in the vicinity of the outer peripheral surface of the rotor 1 increases. Here, the torque for moving the present rotor 1 in the rotational direction is represented by the equation (1), and an increase in the circumferential component of the magnetic flux occurs near the outer periphery of the rotor 1, so that the torque can be increased.

FIG. 3 shows a magnetic flux vector distribution obtained by a magnetic field analysis for the structure of the rotor 1 described above. FIG. 3 shows that the magnetic flux concentrates and flows in from the protrusion 6 at the tip of the rotor salient pole 4, and the magnetic flux of the circumferential component increases. If the tip of the projection 6 is a plane intersecting the rotation direction, it contributes to an increase in torque.

FIG. 4 shows the same magnetic flux vector distribution when the stator 2 and the rotor 1 start to face each other. As shown in FIG. 4, the protrusion 6 due to the structure of the rotor
The magnetic flux that flows in more has a large circumferential component and a large radial distance acting, so that an improvement in torque is recognized.

In the above-described embodiment, the protrusion 6
Is provided in the rotation circumferential direction of the tip of the rotor salient pole, but the shape of this projection will be considered.

FIG. 5 is a side sectional view of a second embodiment of the present invention, in which the length of the protrusion 6 is at least equal to the height at the tip. The aspect ratio of the protrusion is 1
It has become. The rotor salient poles 4 having the projections having such an aspect ratio have a local concentration of the magnetic flux passing through the projections due to the concentration of the magnetic poles on the projections 6 described in the first embodiment. This can be suppressed.

FIG. 6 shows the results of a magnetic field analysis of the magnetic flux lines when the aspect ratio of the protrusion 6 is set to 1.
From FIG. 6, it can be seen that the concentration of the magnetic flux inside the protrusion 6 is reduced. If the protrusion length and height are too small, the effect is small, and if the protrusion length and height are large, the state approaches the state where the protrusion is eliminated. Therefore, it is necessary to appropriately select the dimensions. First, the protrusion is rectangular by numerical calculation, and the ratio of the protrusion length w to the height h (w / h) and the rotor generated torque ratio (torque / protrusion when there is a protrusion FIG. 7 shows a relationship diagram of (torque when there is no torque). It becomes maximum when w / h is 1. The position where the abscissa is 0 and the torque ratio is 1 is when there is no protrusion. It can be seen that the effect is reduced when w / h exceeds 1.7 and becomes elongated. FIG. 7 shows the values when the ratio of the height h of the protrusion to the height H of the rotor salient pole is about 0.13.
When the ratio h / H further decreases, the effect gradually decreases. Even if the ratio h / H becomes too large, the torque component that pulls the rotor in the circumferential direction of rotation decreases, the effect decreases, and the ratio has an optimum range. This range is from 0.05 to 0.3 from FIG.

FIG. 9 is a side sectional view showing a third embodiment of the present invention. The provision of the protrusion 6 at the tip of the salient pole 4 is the same as in the above embodiments, but in this embodiment, the width 9 of the protrusion 6 is changed in the direction of the rotor rotation axis. That is, as shown in FIG.
Are discontinuously changed in the axial direction or continuously as shown in FIG. According to the rotor having such a protrusion, the amount of magnetic flux flowing from the protrusion 6 of the rotor salient pole 4 at the same rotor rotation angle changes depending on the axial position. Therefore, since the vibrations generated in the rotor 1 and the stator 2 at the time of the inflow of the magnetic flux are generated with a time lag, it is possible to greatly reduce the vibration of the entire motor and the noise caused thereby.

FIG. 10 is a sectional side view of a main part of a fourth embodiment of the present invention. In this embodiment, the provision of the protrusion 6 at the tip of the rotor salient pole 4 is the same as that of the above-described embodiment. However, in this embodiment, the tip of the stator salient pole 3 is also provided in the rotation direction. The projection 10 is provided on the opposite side. According to this structure, the magnetic flux that has flowed into the space from the protruding portion 10 at the tip of the stator salient pole 3 contains a large amount of circumferential component, and when the magnetic flux flows into the rotor outer peripheral surface 7 on the side facing the stator salient pole 3. However, since the outflow angle tendency continues, the flow is changed to the inflow magnetic flux flow including many circumferential components. Therefore, an increase in the rotational torque represented by the expression (1) is obtained, and an improvement in efficiency can be achieved. FIG.
Shows a magnetic flux diagram by magnetic field analysis. From FIG. 11, it can be seen that the magnetic flux flowing out from the protrusion 10 provided at the tip of the stator pole 3 flows into the surface 7 of the rotor salient pole 4 while containing a large amount of circumferential components.

FIG. 12 is a side sectional view showing a main part of a fifth embodiment of the present invention. In this embodiment, the rotor salient poles 4
The rotor surface is covered with a non-magnetic material 11 excluding at least the rotor outer peripheral surface 7 facing the stator 2 and the side wall surface 8 having the projection 6 in addition to the rotor shape described above in which the protrusion 6 is provided at the tip. Therefore, the inflow position of most of the magnetic flux on the surface of the rotor salient pole 4 is set at the rotor outer peripheral surface 7 facing the stator.
In addition, since the magnetic flux is limited to the protrusion-side rotor side wall surface 8 and leakage of magnetic flux to other surfaces can be suppressed, an effective force for rotating the rotor 1 can be increased, which can contribute to an improvement in torque.

FIG. 13 is a sectional side view showing a main part of a sixth embodiment of the present invention. Providing the protruding portion 6 at the tip of the rotor salient pole 4 is the same as in the above-described embodiments, but the angle of the connecting portion on the axial side between the protruding portion 6 and the rotor salient pole 4 is made gentle. In addition, the corner 12 is formed thick. The magnetic flux flowing out of the stator salient pole 3 flows into the interior of the rotor 1 from a projection 6 provided at the tip of the rotor salient pole 4, and passes through the inside of the rotor 1 main body. At this time, the magnetic flux is sharply bent at the corner 12, and the magnetic flux density at this point locally increases. Therefore, the saturation of the magnetic flux occurs when the current flowing through the winding 5 is increased during high-speed, high-torque rotation, and the torque decreases. Therefore, when the corner 12 is made thick as shown in FIG. 13, the concentration of the magnetic flux passing through this portion is greatly improved, and the decrease in torque is reduced. FIG. 14 shows a magnetic flux diagram based on the magnetic field analysis. From FIG. 14, it can be seen that the concentration of the magnetic flux at the corners 12 is eased because the axial side roots of the protrusions 6 provided at the tips of the rotor salient poles 4 are thickened.

The provision of the protrusion extending in the rotational direction on the outer periphery of the tip of the rotor salient pole as described above facilitates detection of the rotor position. FIG. 15 is a diagram showing characteristics of the relationship between the winding current and the rotor rotation angle in this case. In the state when the constant voltage pulse is applied, the solid line is the characteristic when the rotor according to the present invention is used, and the dotted line is the characteristic when the conventional rotor as shown in FIG. 16 is used. As shown in FIG. 15, the change in current generated in the winding of the stator in the initial stage of the start of facing between the salient rotor poles and the salient stator poles changes more sharply than in the related art. Conventionally, when detecting this current change and detecting the rotor 1, the current change is small,
Although not suitable for controlling the SR motor, according to the present invention, since the detection accuracy can be greatly improved, it can be used for a sensorless control method, and can greatly contribute to improvement in motor efficiency.

The embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

[0037]

As described above, according to the present invention, magnetic flux intensively flows in from the protruding surface provided in the circumferential direction of the rotor salient pole tip, and the circumferential component of the magnetic flux contributing to torque generation increases. Therefore, the rotational torque is improved.

By appropriately selecting the protrusion length and height of the protrusion provided at the tip of the rotor salient pole, even when the amount of magnetic flux increases, the magnetic flux does not saturate, and therefore the output torque can be increased. The amount of magnetic flux flowing into the protrusion has an effect of reducing the concentration of the magnetic flux, and the generated torque when the energizing current is increased can be improved.

When the length of the protrusion extending in the circumferential direction of the tip of the rotor salient pole is changed in the direction of the rotation axis, a torque fluctuation component can be suppressed.

A protruding portion is provided in the circumferential direction of the rotor salient pole tip, and a protruding portion is also provided in the anti-rotating circumferential direction at the stator salient pole tip to deflect the magnetic flux angle flowing into the rotor surface on the side facing the stator in the circumferential direction. By doing so, the rotational torque is increased.

Since the rotor surface other than the outer peripheral surface facing the stator and the side wall surface having the protrusion is covered with the non-magnetic material, a large amount of magnetic flux generated from the stator flows from the surface that does not cover the non-magnetic material. In particular, an increase in the magnetic flux component flowing from the circumferential end of the rotor tip can improve the rotational torque.

By increasing the height of the root portion of the protruding portion extending in the circumferential direction of the tip of the rotor salient pole, the flow direction of the inflow magnetic flux can be deflected to the salient pole of the rotor without resistance. Therefore, even when the energizing current is increased, the magnetic saturation inside the rotor is reduced, and the density of the magnetic flux flowing into the rotor at the same energizing current increases, so that the rotational torque can be increased.

By providing the protruding portion in the circumferential direction of the tip of the rotor salient pole, the current change generated in the stator winding in the initial stage of the start of the opposition between the rotor salient pole and the stator salient pole changes more sharply than in the prior art. The rotor position can be detected by directly detecting the change. Compared with the conventional sensorless control method, the detection accuracy can be greatly improved, and the effect of ripple superimposed on the current is small, eliminating the need for a circuit to cut off these noises, and high accuracy sensorless control with a simple circuit configuration Can be realized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a first embodiment of the present invention.

FIG. 2 is a sectional view of a main part according to the first embodiment of the present invention.

FIG. 3 is a magnetic flux diagram when the rotor salient poles and the stator salient poles are located at non-opposing positions in the first embodiment of the present invention.

FIG. 4 is a magnetic flux diagram when the rotor salient pole and the stator salient pole start facing each other in the first embodiment of the present invention.

FIG. 5 is a sectional view of a main part according to a second embodiment of the present invention.

FIG. 6 is a magnetic flux diagram in the case of FIG. 5;

FIG. 7 is a diagram illustrating a relationship between an aspect ratio of a protrusion and a torque ratio.

FIG. 8 is a diagram showing a relationship between a ratio between a height of a protrusion and a height of a rotor salient pole and a torque ratio.

FIG. 9 is an axial cross-sectional view of a protrusion according to a third embodiment of the present invention.

FIG. 10 is a sectional view of a main part according to a fourth embodiment of the present invention.

11 is a magnetic flux diagram in the case of FIG.

FIG. 12 is a sectional view of a main part according to a fifth embodiment of the present invention.

FIG. 13 is a sectional view of a principal part according to a sixth embodiment of the present invention.

14 is a magnetic flux diagram in the case of FIG.

FIG. 15 is a diagram showing a change in winding current when the rotor of the present invention is used.

FIG. 16 is a sectional view of a conventional SR motor.

FIG. 17 is an explanatory diagram of torque generated in a rotor of a conventional SR motor.

FIG. 18 is an example of a magnetic flux diagram in the case of FIG. 17;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rotor 2 Stator 3 Stator salient pole 4 Rotor salient pole 5 Excitation winding 6 Projection (rotor salient pole tip) 7 Rotor salient pole outer peripheral surface 8 Rotor salient pole side wall face 9 Projection width 10 Projection (stator salient pole tip) DESCRIPTION OF SYMBOLS 11 Non-magnetic material 12 Corner 13 Control circuit

Claims (8)

[Claims] 1. A switched reluctance motor in which an exciting winding wound around a plurality of stator salient poles provided on a stator is sequentially energized to attract a rotor salient pole provided on a rotor to rotate the rotor. A switched reluctance motor characterized in that the tip of the rotor salient pole has a protrusion extending in the circumferential direction on the rotation side and the tip is flat. 2. The switched reluctance motor according to claim 1, wherein the ratio of the height of the protrusion to the height of the rotor salient pole is 0.05 to 0.3. 3. The switched reluctance motor according to claim 1, wherein the ratio of the length of the protrusion to the height of the protrusion at least at the tip is in the range of 1 + 60% and -80%. 4. The switched reluctance motor according to claim 1, wherein the length of the projection is changed in the direction of the rotation axis. 5. The switched reluctance motor according to claim 1, wherein a tip of the stator salient pole facing the motor has a flat projection at a tip opposite to a rotation direction. 6. The rotor according to claim 1, wherein at least a rotor surface excluding a side surface facing the stator and a side wall surface having a protrusion is covered with a non-magnetic material. Switched reluctance motor. 7. The switched reluctance motor according to claim 1, further comprising a rotor in which a shape of a connecting portion between the protrusion and the shaft side of the rotor side wall is formed smoothly. 8. The switched reluctance motor has a protrusion at the tip of the rotor salient pole that extends in the circumferential direction on the rotation side, and the tip is flat, and the stator salient pole and the rotor salient pole start to face each other. A method for controlling a switched reluctance motor, wherein a position of a rotor is detected by detecting a current flowing through a winding wound around a stator salient pole at a position.